Certain thienopyrimidine derivatives are useful for the inhibition of PDE10 enzymes, and thus are useful for treating psychiatric or neurological syndromes, e.g., pyschoses, obsessive-compulsive disorder and/or Parkinson's disease, as well as, for example, treating a disease state modulated by PDE10 activity.

5. A compound according to claim 1 wherein R.sup.2 is chosen from --O-arylene-Y--R.sup.5, --X(CR.sup.3R.sup.4).sub.nYR.sup.5 and --(CR.sup.6R.sup.7).sub.mYR.sup.5.

6. A compound according to claim 5 wherein R.sup.2 is --X(CR.sup.3R.sup.4).sub.nY--R.sup.5.

7. A compound according to claim 5 wherein R.sup.2 is --O-arylene-Y--R.sup.5.

8. A compound according to claim 7 wherein R.sup.2 is --O-phenylene-Y--R.sup.5.

9. A compound according to claim 8 wherein the --O and --YR.sup.5 substituents attached the phenylene group are meta-substituted.

10. A compound according to claim 5 wherein R.sup.2 is --(CR.sup.6R.sup.7).sub.mYR.sup.5.

11. A compound according to claim 1 wherein X is --NH--.

12. A compound according to claim 1 wherein X is --O--.

13. A compound according to claim 1 wherein Y is --O--.

14. A compound according to claim 1 wherein Y is --NH--.

15. A compound according to claim 1 wherein n is chosen from 3, 4, and 5.

16. A compound according to claim 1 wherein m is chosen from 3, 4, and 5.

17. A compound according to claim 1 wherein R.sup.3 and R.sup.4 are independently chosen from H, CH.sub.3, and F.

18. A compound according to claim 1 wherein R.sup.6 and R.sup.7 are independently chosen from H, CH.sub.3, and F.

19. A compound according to claim 1 wherein --(CR.sup.6R.sup.7).sub.mY--R.sup.5 is --(CH.sub.2).sub.4--O--R.sup.5.

20. A compound according to claim 1 wherein --X(CR.sup.3R.sup.4).sub.nY--R.sup.5 is chosen from --NH--(CH.sub.2).sub.3--O--R.sup.5, --NH--(CH.sub.2).sub.2--NH--R.sup.5, --O--(CH.sub.2).sub.2--O--R.sup.5, --O--(CH.sub.2).sub.3--O--R.sup.5,--O--CH.sub.2--C(CH.sub.3).sub.2--CH.sub.2--O--R.sup.5, and --NH--(CH.sub.2).sub.2--O--R.sup.5.

21. A compound according to claim 20 wherein --X(CR.sup.3R.sup.4).sub.nY--R.sup.5 is chosen from --NH--(CH.sub.2).sub.3--O--R.sup.5 and --O--(CH.sub.2).sub.3--O--R.sup.5.

22. A compound according to claim 1 wherein the compound of Formula I is chosen from compounds of Formula (Ia): ##STR00147## wherein: R.sup.2 is chosen from X(CR.sup.3R.sup.4).sub.nYR.sup.5 and --(CR.sup.6R.sup.7).sub.mYR.sup.5; and Y ischosen from O, S, and NR.sup.9.

33. A compound according to claim 1 wherein R.sup.1 is chosen from phenyl and phenyl substituted by halo, and R.sup.2 is chosen from --NH--(CH.sub.2).sub.3--O--R.sup.5, --NH--(CH.sub.2).sub.2--NH--R.sup.5, --O--(CH.sub.2).sub.3--O--R.sup.5, and--NH--(CH.sub.2).sub.2--O--R.sup.5.